1. Field of the Invention
This invention relates to an apparatus and a method for bending and tempering glass sheets, and more particularly concerns bending glass sheets by dropping a heated glass sheet to a bending mold where the glass sags or bends by gravity to conform to the shape of the mold.
2. Description of the Prior Art
Many technques for bending glass sheets are known. A simple technique is to heat a sheet of glass while supporting the glass sheet on a contoured mold to permit the glass sheet to sag to conform to the shape of the mold. This process is slow, but can be speeded-up by applying a mechanical bending force such as by pressing the glass between a pair of contoured molds, as disclosed by Seymour in U.S. Pat. No. 3,846,104.
U.S Pat. No. 3,476,540 to Ritter et al. discloses a glass bending arrangement whereby a single vertically-rising lower bending mold effects the bending of the glass through the inertia of the glass. Disadvantageously, the bent glass sheets must pass without edge support along a roller conveyor into a tempering zone.
U.S. Pat. No. 3,600,150 to Rougeux shows a glass bending arrangement where the heat softened glass sheet is slipped from a roller conveyor onto a flexible hammock and thereafter press-bent between upper and lower forming molds. The purpose of the flexible hammock is to support the glass sheet initially out of contact with the rigid shaping mold surfaces. It is apparent that a major reconstruction of the apparatus would be required when a change in the glass shape is desired.
U.S. Pat. No, 4,300,935 to Seymour discloses a glass bending arrangement wherein a heat softened glass sheet is elevated by a flat vacuum platen that raises the glass sheet to an elevated position and drops the glass sheet onto a bending mold to effect the bending. The bending mold is passed into a tempering station by a shuttle where the glass sheet is tempered.
A problem with prior art glass bending systems has been to provide a system that can be easily adapted to bend different shapes and sizes of glass.
Another problem with the prior art glass bending systems is the heated glass sheets begin to cool as soon as they leave the oven before they are bent, which can affect the quality of the glass bending.